How and Why Value Add Basketball Ratings Work So Well

22 Jan 2013

For an explanation of the Value Add basketball rankings, you can always click on this post from the bottom of the www.valueaddbasketball.com database. I must thank Sports Illustrated, ESPN, NBC Sports and all of the other outlets who have covered Value Add. Moving forward, the ratings will be released first on Breitbart and then updated back on the Value Add site to allow for sorts. A variation of this formula measures how likely a player is to be successful in the NBA, but the basic explanation of how and why it works follows.

Anthony Davis added 7.29% to Kentucky’s scoring with his offense, and took away -5.06% from opponent’s scoring, so his total impact on the score was 12.35%, the highest Value Add in the country in 2012. This means that if Kentucky would have lost a game 69-70 with a typical fourth or fifth man off the bench playing instead of Davis, then with Davis they win 74-66.

When you first pull up the database at www.valueaddbasketball.com, you will see the ratings of all of the basketball players for this season. You can search by team, conference or a player’s name to see where specific players rank, or just scroll through more than 3000 players for each season.

You can also click on the other tabs to see players from the 2006 season through the projections for how good players should be in 2014, including new recruits. This is probably enough explanation for most readers, but if you want more details, the ratings consist of three components:

1. The Offensive component is explained in this post, as we can measure with great precision how many points a player ad to his team’s score.

2. The Defensive component is not quite as precise, but measures a player’s ability to block shots, steal the ball, grab defensive rebounds and be part of a defense that prevents opponents from scoring in other ways. In both cases, a players rating is measured against exactly how good each of an opponents’ offense and defense is, so the same player should have basically the same rating whether he plays for the national champion or the worst Division 1 team.

3. The Point Guard/Perimeter Defensive Rating (PG/Per) redistributes a small percent of the credit from post players who do not turn the ball over as much because they do not have to dribble as often and who grab more defensive rebounds because they do not have to play defense on the perimeter. After extensive study, this figure was determined the most accurate way to fairly adjust ratings based on position, as explained in this post.

NBA Indicators Developed by Rob Lowe

Much like Ken Pomeroy at www.kenpom.com, Rob Lowe (who is much smarter than me) developed methods for measuring tempo free statistics as calculated in Dean Oliver’s book, “Basketball on Paper.” While Oliver, and in turn Pomeroy, determined how to measure a dozen things a player does to help his team win, www.valueaddbasketball.com instead breaks down all ways a player helps his team into on figure that determines his overall value.

Lowe built on Value Add and other sources to develop calculations that measure how likely a player is to be successful in the NBA, and officials from several NBA teams met with me prior to the 2012 draft to review these valuations. These evaluations are only available to select NBA teams, but we plan to provide real-time coverage of the NBA Draft (see last’s years first round and second round) as picks are revealed at Breitbart Sports.

Others have built on the Value Add system since it was developed. Sports Illustrated used it to go back further in history and conclude that Duke’s JJ Reddick was the best Value Add guard since modern stats were introduced, and that research was picked up by ESPN. Basketball Prospectus then started to add to the equation with some additional calculations.

Big Apple Buckets out of New York was instrumental in the further development of a variation to calculate the value of players in the Ivy League and other low major conferences, and we have received follow-up questions from Ivy League schools and officials. These ratings can be found by clicking on the “Low-Major” link in the bottom right corner.

One credibility test for the system occurred after an engineer developed the program to run the calculations, and a Marquette player, Jae Crowder, showed up as an All-American. Statisticians never like to have a favorite when running numbers, and the fact that I covered Marquette and Crowder’s Value Add was so high even though he was not even an All-Conference player nor listed in the top 100 NBA prospects made me nervous. However, several NBA team officials met with me and were very complementary that my calculations were “finding” several of the same sleeper prospects they had found through intense scouting, including Crowder.

I did later meet Crowder after his last game at Marquette, and was put at ease months later when the AP sports writers named him one of the top 10 players as a second team All-American and then the Dallas Mavericks drafted him and he was named named an All-Star in Summer League and made the Mavs. While the numbers were backed up, I will give Crowder and the other players who backed up their Value Add ratings with great runs on the court assists for the success of Value Add.